When the old car drowns out in the stream crossing, there is a set of wet tire tracks exiting the stream ahead of the old car.
The seven-shot six-shooter: Joe Knox and Billy (Oliver Reed and Strother Martin) are cavorting on a large log that has fallen across a creek. Sam Longwood (Lee Marvin) pulls out his revolver and shoots at them, clearly firing off seven shots from a six-shooter revolver.
When Sam was chasing the wagon driven by Thursday, he falls down and his hat is missing. In the next scene, showing Thursday driving and Sam getting up in the background, his hat is on his head as he gets up.
When Thursday drives off in the wagon and Billy falls off, the mat on the ground that breaks his stunt double's fall is visible.
In the counting wagon there is a small American flag with 50 stars. In 1908 (the year of the film) there would have been 45 stars, or if the flag was brand new it would have had 46 stars on account of Oklahoma joining the Union the year before.
The flag in Sam's vendors uniform cap has 50 stars on it.
The song at the end of the movie sings of 'Jennings Bryan, the pride of the Bible Belt.' The movie takes place in 1908. The phrase 'Bible Belt' was coined in 1917, by H.L. Mencken in his article, 'Puritanism as a literary force.'
When Sam officially reunites with Jack, some of the flags at the party are the rare 49 star flag, which was in existence from 1959-1960.